Preparation And Environmental Application Of Carbon Based Quantum Dot Materials

Carbon is a new kind of luminescent nanomaterials in recent years,because of its size,generally less than 10 nm,and carbon points has its unique physical and chemical properties,good biocompatibility and stability,the advantages of low cytotoxicity,water-soluble,and with the launch of tunable,stable photoluminescence excellent optical properties,etc.Carbon dots have broad application prospects in biological imaging,ion detection,drug delivery and optoelectronic devices.In this paper,the CDs solution has the advantages of versatility,spectral properties,easy modification and high sensitivity,and is applied to the detection of ferric ions and p H.The main research contents are as follows:In the first part,bean sprout was used as carbon source and water was used as solvent to prepare bean sprout carbon points by hydrothermal synthesis.The carbon dot shows a bright blue fluorescence.The CDs were characterized and their possible formation mechanism was discussed.Due to the soluble functional groups on its surface,it has good dispersibility.The quantum yield(QY)of the prepared carbon dots was 9.25%.In the linear range of 1?100?M,the fluorescence of CDs was quenched by Fe³⁺with a detection limit of 0.37?M.Through interference studies,it was found that the addition of metal ions did not affect the selectivity of CDs to Fe³⁺.These results indicate that the newly synthesized CDs have selectivity and sensitivity for the determination of Fe³⁺by fluorescence shut-off method.In the second part of the study,p H-responsive CDs was synthesized with citric acid and urea as precursors,and its fluorescence intensity increased gradually with the p H value of the solution increasing from 1 to 12.A new mechanism based on H-aggregation and Fermi level shift is proposed to illustrate the p H-responsive emission of CDs.The mechanism of p H response was studied,and it was found that H-aggregation of CDs occurred in acidic solution,which led to the red fluorescence quenching of carbon spots When carbon dots are dissolved in alkaline solution,the Fermi level shift leads to a decrease in self-absorption,and the fluorescence of carbon dots is enhanced.Different from the narrow response range of the most reported p H-sensitive CDs,CDs have a wide p H response range,especially in the alkaline range,and their obvious red light emission clearly achieves a good visualization effect.The prepared carbon dots have the advantages of non-toxicity,low cost,and wide p H response range.In addition,"rose filter paper"was made to show the visualization of carbon dots used to detect p H.In addition,a composite film of carbon dots and PVA was also made,and the carbon dots composited with PVA still had good fluorescence intensity.The prepared carbon dots have broad application prospects in p H detection.In summary,two new types of CDs were synthesized by hydrothermal method.Among them,the CDs with blue fluorescence emission can be used for the detection of Fe³⁺,and the CDs with red fluorescence emission can be used for the qualitative analysis of p H.It has great application value in detection and p H value detection,and also provides new ideas for environmental detection,which has a positive impact.